This invention pertains to a process for the production of molecular nitrogen (N.sub.2) from combustion gases by utilizing membranes to achieve the separation of the nitrogen from the other molecular constituents present in such combustion or stack gas streams.
Nitrogen has many commercial uses. The oil, gas, and chemical industries require large volumes of the gas. The most widely used commercially available process for the production of large volumes of nitrogen is based on the cryogenic separation of nitrogen from air. This process, which has been practiced for over 30 years, has probably reached its efficiency peak, because of high cost, other technologies have been investigated but have been limited to smaller-volume applications, where cost is not crucial.
Membranes can be used to preferentially separate a desired gaseous molecule from a mixture of other gases molecules under specified conditions, based on the respective gas permeabilities through a specific membrane. A specific membrane, or combinations of different membranes with different gas permeabilities, can be customized through the selection of the membranes used and the configuration (parallel or series) selected to achieve the desired separation. Since membrane modules have no moving parts, they are ideal for unattended operation. In addition, the physical properties of the membrane plants, such as size and weight, make possible a portable production facility. This is not feasible with cryogenic separation. In consequence, production of nitrogen by the use of membranes can offer significant advantages over other known nitrogen-production systems.